'Sister Wives': Kody Admits Living in 'Delusional World' Where He Wishes Christine Wouldn't Leave (Exclusive)

In a preview clip, the family enjoys celebrating Ysabel's milestones, prompting the family to ask why it can't always be that way.

It was quite the perfect day when the Brown family celebrated Ysabel's graduation and birthday. The entire brood laughed, mingled and enjoyed each other's company as they indulged on cake, gluten-free quiche and basked in the splendid Arizona weather, which all the more begged the question -- why would Christine Brown choose to leave all of this behind?

In an ET exclusive preview clip of Sister Wives, that's exactly the dilemma Kody Brown and his wives -- Meri, Janelle and Robyn Brown -- find themselves in wake of Christine's decision to split from Kody after nearly three decades together and six children. Kody, for the life of him, can't fathom how Christine can move forward with her plan after such a blissful day.

It's so unfathomable to him, Kody admits celebrating Ysabel's milestone left him feeling like he's living in a "delusional world." And, yes, it's all making him sad.

"This evening has gone off without a hitch. It’s been wonderful, and I think Ysabel has felt special," Kody says in the preview clip. "I’m just blue. We will never be there again. If we really go through with this is, as Christine is leaving, is she really going to leave? I’m living in a delusional world where [I’m] wishing that Christine wouldn’t leave."

The entire brood's gathered around outside their Arizona compound enjoying a trampoline sesh and plenty of sweets in honor of recent high school grad Ysabel. The day's gone so smooth, Robyn echoes Kody's sentiments.

"We’re in this moment, we’re having a nice time, how is this wrong? How does this not work for everybody?" she asks. "Why isn’t this something worth fighting for? Why isn’t this something worth staying for? I don’t know, I’m just one of those people who hopes, constantly, that maybe something will spark for someone and go, 'Oh, this is worth figuring out, sticking around,' [because] I would look at it and think that. It could make Christine feel like, ‘Hey, this is worth staying for.'"

Meri offered similar thoughts, while also wondering if Christine leaving is truly the best decision for the family.

"You know, when I look at days like this when we’re all together, and we’re all smiling and setting the crap aside like, why can’t we do that?" she asks. "Why can’t we work on the things that we need to work on between each other? We’re not doing justice to our family ... I’m devoted to doing what I need to do. I know that not everybody is."

Janelle, on the other hand, admits that while the day proved heavenly, she just doesn't see how they can sustain the feeling.

"I personally am not very optimistic that we'll see very many days like this," she opined.

As for Christine, she feels Kody's finally realizing he let too much time pass him by without strengthening his bond with Ysabel.

"Kody is not one to hide his emotions," Christine says. "He's more, like, gonna show you how he's feeling, and I think he's just super sad. And it's bittersweet. He loves Ysabel. And he hasn't spent enough time with her, and I think he's probably realizing that."

It was during last week's episode when Christine finally told her fellow sister wives that she's planning to leave Kody. Meri wasn't happy about it. In fact, she was angry, as was Robyn. Jenelle, however, wasn't surprised by Christine's decision, citing their long history. 

It all leads to Kody having a stern face-to-face discussion with his wives about what he expects moving forward.

"I'm going to be the head of my household again and so I'm not going to be circumvented in that," Kody declared. "And so if everybody's willing to conform to patriarchy again, I guess, because I've been fighting to make everybody happy. My bitterness is that out of trying to do that and not having the family that I had thought about and designed."

"If it's too awkward or I don't feel like I'm the head of my household when people are around then I'm not going to have the whole family together," he added. "I'm at the point now in my life where I don't have time to waste on people who won't respect me or treat me with respect, so we'll see how that goes." 

Sister Wives airs Sunday at 10 p.m. ET on TLC.